1. Field of the Invention
The present invention relates, in general, to a method of forming the chip bumps of a bump chip scale semiconductor package, and to such a package and chip bump and, more particularly, to an improvement in such a method, package and chip bumps for directly mounting a semiconductor chip to a mother board by forming the chip bumps on the chip pads of the semiconductor chip.
2. Description of the Prior Art
The recent trend of compactness, smallness, lightness, thinness and multi-function of semiconductor-electronic appliances is promoted by high integration and high effectiveness of semiconductor chips. In order to meet such a recent trend, it is necessary to achieve compactness, smallness, lightness and thinness of semiconductor packages and to maximize the number of fins of each package. That is, it is necessary to reduce the size of the packages while improving the operational function of the packages. In this regard, the packages using solder balls as the signal input and output terminals are preferred to the packages using leads as the signal input and output terminals.
A BGA (ball grid array) semiconductor package, which is a typical package using the solder balls as its signal input and output terminals, remarkably reduces the package size and remarkably improves the integration degree of the package in comparison with a typical QFP (quad flat package). However, the typical BGA package is problematic in that it fails to effectively reduce the package size due to the molding zone thus regrettably requiring a large surface mounting area when it is mounted to a mother board. Therefore, such a BGA package fails to achieve compactness, smallness, lightness and thinness of semiconductor-electronic appliances.
FIG. 9 is a sectional view showing the construction of a typical BGA package. As shown in the drawing, the BGA package comprises a semiconductor chip 1 which is attached to the top center of a PCB (printed circuit board) 7 by epoxy resin. The PCB 7 has a circuit pattern 71 on its edge portion. The chip pads of the semiconductor chip 1 are electrically connected to the circuit pattern 71 of the PCB 7 through a plurality of wires 8. A predetermined molding zone including the chip 1 and wires 8 is packaged by a molding compound 9 thus protecting the chip 1 and wires 8 from the atmosphere. A plurality of solder balls 2 are formed on the bottom side of the PCB 7 and are used as signal input and output terminals of the package.
As described above, the typical BGA package uses the wires 8, so that the area of the package is enlarged due to the wire loop thus reducing the package density while surface-mounting the packages. In addition, it is difficult to design the circuit pattern on the mother board due to the enlarged area of the package. Another problem of the above BGA package resides in that interfacial separation may be generated in the junction between the parts of the package due to a change of temperature.